import java.util.Scanner;

public class a148_You_Cannot_Pass {

	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		
		String str1;
		String[] sp;
		
		int m; // 有幾個科目
		Double sum;
		
		while(input.hasNext()) {
			str1 = input.nextLine();
			sp = str1.split(" ");
			
			m = Integer.parseInt(sp[0]); // line : 11
			
			// 從sp[1]開始
			sum = (double)0;
			for(int i = 1; i < sp.length; i++) {
				sum += Integer.parseInt(sp[i]);
			}
			
			//output result
			if(Math.round (sum / m) > 59)
				System.out.println("no");
			else
				System.out.println("yes");
		}
	}
	
}